Echogenic needle catheter configured to produce an improved ultrasound image

ABSTRACT

An echogenic medical device, such as a needle catheter, which produces an improved ultrasonic image of the device, and a method of performing a medical procedure using a device of the invention. One aspect is directed to a catheter which reduces artifacts in the ultrasound image of the catheter. In one embodiment, the catheter has a spherical distal tip. Another aspect of the invention is directed to an echogenic catheter with echogenic portions arranged in an array to facilitate determination by ultrasonic imaging of the rotational orientation of the catheter relative to a desired location within the patient.

This application is a divisional of U.S. patent application Ser. No.11/293,420, filed on Dec. 2, 2005 now U.S. Pat. No. 7,867,169.

BACKGROUND OF THE INVENTION

The invention relates to the field of medical devices, and moreparticularly to echogenic catheters, such as needle catheters.

An essential step in treating or diagnosing cardiac tissue orcardiovascular diseases using an interventional catheter is the properplacement of the catheter at a desired location within the patient,which consequently requires accurate imaging of the catheter locationwithin the patient. Although various methods of imaging catheters withina patient are possible, ultrasonic imaging (also referred to as acousticimaging) would provide several advantages. For example, ultrasonicimaging is very safe for the expected extended time periods required fortherapy guidance, unlike CT/EBCT (Electron Beam Computed Tomography) orbi-planar fluoroscopy. Additionally, ultrasound is relativelyinexpensive compared to other imaging modalities such as MRI or CT/EBCT,and can provide tissue diagnostics such as wall motion and thicknessinformation.

However, one difficulty is visualization anomalies, including artifactsand overly bright images, in the ultrasonic images of catheters. Suchartifacts can provide a misleading and inaccurate impression of theshape and/or location of the catheter within the patient. Additionally,catheter elements can appear so bright and large on the ultrasonic image(called “blooming”) due to their highly reflective nature relative tothe anatomy, especially at the gain settings typically used to image theanatomy, that the image of the adjacent anatomy is obscured by thecatheter image. For example, metallic portions of catheters can producestrong/high amplitude echoes (bright images), with a pyramid artifact(i.e., a pyramid shape of reverberation (“ringing”) images trailing offin the viewing direction). Similarly, most thermoplastic catheter shaftsproduce strong/high amplitude direct echoes (bright images). If the gainsettings of the ultrasonic imaging system are reduced to improve theimage of the catheter (reduce its image and artifact brightness), theimage of the anatomy fades significantly to the point of being lessvisible or not visible at all. Therefore, it would be a significantadvance to provide a catheter with improved imaging characteristics bytwo-dimensional and three-dimensional ultrasonic imaging systems forenhancing the diagnosis and guidance of treatments in the body.

SUMMARY OF THE INVENTION

The invention is directed to an echogenic medical device, such as aneedle catheter, which produces an improved ultrasonic image of thedevice, and a method of performing a medical procedure using a device ofthe invention. One aspect is directed to a catheter which reducesartifacts in the ultrasound image of the catheter. In one embodiment,the tip of the catheter is directly imaged over a range of angles(relative to the catheter) substantially greater than 180°. Anotheraspect of the invention is directed to an echogenic catheter shaftconstruction, in which the amplitude of the direct echoes produced bythe catheter shaft are reduced, and/or in which diffuse echoes areproduced that facilitates the imaging of the catheter portions that donot produce a direct echo. Another aspect of the invention is directedto an echogenic catheter in which the imaging of a portion of thecatheter reveals the rotational orientation of the catheter relative tothe imaging direction.

In one embodiment, the echogenic needle catheter has a spherical distaltip which reflects sonic energy more diffusely than a non-sphericaldistal tip. Non-spherical tips on catheters are capable of directlyreflecting sonic energy back to a transducer of an ultrasonic imagingdevice over range of angles of not greater than about 180° relative tothe longitudinal axis of the catheter. For example, catheter tips havinga rounded distal end allow for direct ultrasonic imaging of the cathetertip only from the distal front of the catheter tip up to about 90° orperpendicular to each side of the catheter tip. Beyond this range, thenon-curved portion of the non-spherical tips are shielded from the sonicenergy by the catheter body or produce sonic reflections that do notreturn directly to a transducer of an ultrasonic imaging device. Thus,unlike a spherical distal tip of the invention, conventionalnon-spherical distal tips on catheters can't be directly imaged fromsubstantially behind the catheter tip.

The spherical distal tip of the invention includes a spherical portionor portions that produce direct sonic reflections back to a transducerof an ultrasonic imaging device from a range of angles greater thanabout 180° (i.e., from a range of angles which extend from in front ofto behind the catheter tip). The spherical shape is preferred for thedistal tip because the spherical shape will directly reflect sonicenergy at substantially the same amplitude over its direct reflectionrange of angles and will not have the higher amplitude and largeramplitude range of reflected echoes seen from flatter tips or thecylindrical portions of rounded tips. The spherical distal tip thusallows the tip to produce a direct ultrasonic image from a greater rangeof angles relative to the catheter than conventional tips. Specifically,the tip directly reflects the sonic energy back in the direction of atransducer of an ultrasonic imaging device, with the catheter located ata wide range of angles relative to the viewing direction of theultrasonic imaging device. As a result, the distal end of the cathetercan be manipulated, such as by tendon deflection or insertion into avessel, and positioned at a greater range of angles within the anatomyyet still have its distal tip reliably imaged by an ultrasonic imagingsystem. Additionally, the spherical shape of the distal tip isatraumatic to prevent or inhibit disadvantageously injuring thepatient's anatomy.

In a presently preferred embodiment, the spherical distal tippedechogenic needle catheter is configured for percutaneous transluminaladvancement into a chamber of the patient's heart, although a variety ofalternative catheter configurations may be used. The echogenic needlecatheter generally comprises an elongated shaft having a proximal end, adistal end, and a needle lumen extending therein, with the sphericaldistal tip at the distal end of the elongated shaft, and a needleslidably disposed within the needle lumen of the catheter. In apresently preferred embodiment, the spherical distal tip has a lumen incommunication with the needle lumen of the shaft and with a port in thein the spherical distal tip which is configured for having the needleslidably extend therethrough. The needle disposed within the cathetershaft has a distal end which extends distally from the spherical distaltip port in an extended configuration.

In a presently preferred embodiment, the spherical distal tip is formedat least in part of a conductive material to function as an electrode.The spherical distal tip electrode is formed at least in part of ametallic material. The metal in the spherical distal tip allows the tipto function as an electrode, primarily for diagnostic purposes, but,alternatively, for therapeutic purposes (e.g., defibrillation), ifdesired. Additionally, in one embodiment, the tip formed in part of ametallic material is configured to produce a tip pyramid artifact of adesired brightness and duration, as discussed in more detail below. Insome embodiments, the presence of the pyramid artifact at a reducedlevel relative to conventional fully metallic distal tip electrodes isdesirable to more reliably differentiate the image of the catheter tipfrom the image of the catheter body and thus indicate that the tip ofthe catheter is being imaged, but in a manner that doesn't substantiallyobscure the image of the adjacent anatomy.

Prior non-spherical distal tip electrodes reflect a large amplitudedirect echo and often a large range of echo amplitudes over the range ofdirect reflecting angles, such that at angles behind the tip a directecho does not return in the direction of the ultrasonic imaging deviceprobe and, therefore, does not produce a direct image. In contrast, thespherical distal tip electrode of the invention more diffusely andevenly reflects ultrasonic energy. As a result, the spherical distal tipelectrode can be imaged from a greater range of angles relative to theviewing direction of the ultrasonic imaging device (e.g., a range ofangles greater than 180°; compared to a range of angles of not greaterthan about 180° for a conventional rounded end distal tip). Also, theecho amplitude of the tip is smaller and less variable over its range ofimaging angles than a non-spherical metallic tip.

A catheter distal tip formed at least in part of a metallic materialabsorbs, stores and then reemits the sonic energy of the ultrasonicimaging device, causing the metal in the tip to ring like a bell,sending out ultrasonic energy until the sonic energy that it has storedis depleted. This absorbed, stored and then reemitted sonic energy isreceived by the ultrasonic imaging device and creates images behind thecatheter tip that decrease in brightness and size as the stored sonicenergy is depleted, forming the tip pyramid artifact. On the other hand,polymeric materials produce echoes from their surfaces in the body thatare usually of less amplitude than the thick metallic surfaces ofconventional electrode tips. Additionally, polymeric materials aregenerally more dissipative of sonic energy than metallic materials andthus, if any pyramid artifact is produced, it is of smaller amplitudethan those produced by completely metallic tips. In one embodiment, thepresence of the artifact is desirable to indicate that the tip of thecatheter is being imaged. However, a disadvantageously bright/longduration/large tip pyramid artifact obscures the actual image of thecatheter tip and surrounding anatomy. A distal tip of the invention,configured to minimize the amount of metallic material at the distaltip, reduces the amount of sonic energy that the tip stores and thenreemits to thereby reduce the brightness and duration of the tip pyramidartifact. Additionally, in one embodiment, the spherical distal tip isin contact with a damping (sonic energy dissipating) material, such asmany plastic/epoxy/elastomeric compounds and mixtures, which may containair bubbles, tungsten filings and the like, to reduce the brightness andduration of the tip pyramid artifact. For example, in one embodiment,the spherical distal tip is filled with the damping material, and/or isconnected to a proximally adjacent section of the shaft formed, at leastin part, of the damping material.

In the absence of a direct echo from the tip, the only ultrasonic imageof the tip may be that due to the absorbed, stored and then reemittedsonic energy and that image is located behind the actual location of thecatheter tip (due to the delay in reemitting the sonic energy in thedirection of the imaging device). As a result, the direct echoesproduced by the spherical distal tip of the invention, from a largeangular range, prevent or minimize the potential for misreading theposition of the distal tip from the ultrasonic image, by avoiding theabsence of an imaged direct echo from the distal tip.

In a presently preferred embodiment, the spherical distal tip is formedin part of a plastic/polymer material or materials, to minimize theamount of metal in the tip and thus reduce its echo amplitudes andreduce or eliminate its pyramid artifact. In one embodiment the distaltip has a plastic/polymer wall formed of a material selected from thegroup consisting of an epoxy, a polyurethane, a silicone, apolyethylene, and an ethylene acrylic acid functionalized polyolefinsuch as PRIMACOR. In a presently preferred embodiment, the tip is formedat least in part of an adhesive polymer such as PRIMACOR to assure thesecure bonding together of metals to polymers or polymers to polymers inmany configurations of the spherical tip, especially bondingplastics/polymers to metallic components such as hypotubes, metal shellsor to thin coatings/platings of metallic conductors. Adhesive polymersmay be incorporated into a spherical tip assembly in a number of ways.For instance, adhesive polymers may be mixed with another polymer toprovide that polymer with adhesive characteristics or the adhesivepolymer may be put into solution and applied to a surface (i.e. bydipping, spraying, brushing), such that when the solvent evaporates, athin coating of the adhesive polymer is deposited on the surface toprovide an adhesive surface for further processing. The adhesivefunction of the adhesive polymers is often enhanced by raising thetemperature of the adhesive polymer for a short time (i.e. during amolding or forming process, as part of a conditioning cycle) and, thusare often referred to as “hot melt adhesives”.

For example, in one embodiment, the spherical distal tip includes ametallic member therein with an exposed surface to function as anelectrode. In another embodiment, the spherical outer surface of the tipis defined by a wall formed of a mixture of blended or otherwisecombined polymeric and metallic materials. In another embodiment thespherical tip is formed of a polymeric material or materials and/or amixture of polymeric and metallic materials and at least a portion ofits outer surface is a thin metallic layer or layers, which may bedeposited or attached by various conventional methods (i.e. sputtering,deposition processes in chemical solutions, pressure bonding). However,a variety of suitable configurations can be used, including a sphericaltip formed of a wall of metallic material (although a metallic wallpreferably defines a spherical interior chamber to minimize the amountof metal in the tip and thereby reduce the brightness and duration ofthe tip pyramid artifact). In embodiments in which the wall of thespherical distal tip defines a spherical interior chamber, the chamberis preferably filled with a polymeric material.

In a presently preferred embodiment, the spherical distal tip comprisesa wall with a curved outer surface formed at least in part of apolymeric material and having a metallic pin member therein, or having ametallic outer layer thereon.

In one embodiment, an element(s) formed at least in part of a metallicmaterial such as an additional conductive electrode(s) or marker(s)provided on the shaft is proximally spaced a sufficient distance fromthe spherical distal tip that the ultrasonic images produced by theseadditional metallic elements do not overlap with those of the sphericaldistal tip. As a result, the catheter of the invention facilitatesaccurately interpreting the spherical distal tip's position in theultrasonic images. Such additional electrodes or markers may also beconstructed of a limited amount of metal and/or in contact with sonicenergy damping materials to provide the same brightness and artifactreduction benefits as previously described in relation to the sphericaltip.

In one embodiment, a catheter of the invention has an outer jacket layeralong at least a portion of the catheter shaft, formed of an impedancematching material of approximately a quarter or three quarter wavelengththickness. In one presently preferred embodiment, the layer has aquarter wavelength thickness in order to maximize the destructiveinterference. However, because the ultrasonic pulse waveform sent out bymany echo probes is often many wavelengths long, a three quarterwavelength thickness will also produce destructive interference and canbe reasonably effective in reducing the amplitude of reflected sonicenergy. For example, in an embodiment in which the center frequency(imaging ultrasonic transducers typically send out sonic pulses thatcontain a spectrum of sonic frequencies) of the displayed echoes is highand/or the speed of sound in the material is too low, then the materialthickness of the jacket might be too small to be efficientlyproduced/installed at a quarter wavelength thickness. For example, at 6MHz, silicone has a quarter wavelength thickness of about 0.0015″, whichmay be difficult to process/control, but has a three quarter wavelengththickness of about 0.0045″, which facilitates accurately producing theouter jacket layer. Echo TTE and TEE systems, applicable to thistechnology, are advertised to operate in frequency ranges that go fromabout 1 MHz to 12 MHz, and a typical cardiac transducer (probe) isadvertised to operate in a 2-4 MHz range or in a 3-8 MHz range.

The outer jacket layer is formed of a material with an acousticimpedance which more closely matches that of blood than does thematerial(s) forming the portions of the catheter shaft underneath theouter jacket layer. “Acoustic impedance” is a material property whichmay be defined as the velocity of sound in that material multiplied bythe density of the material. For example, in one embodiment, the outerjacket layer is formed of a polymer selected from the group consistingof elastomeric polymers, low density polyethylene (LDPE), and ethylenevinyl acetate (EVA), and the underlying catheter shaft comprises ametallic braid or other metallic configuration, and/or a high acousticimpedance polymer or thermoplastic polymer more commonly used to formcatheter shaft outer surfaces, e.g., nylons, Pebax, polyethylenes,polyesters, etc. In some embodiments, the outer jacket is coated with alubricant (i.e. silicone oil based coatings like MDX) or a hydrophilicor a hydrogel coating to substantially reduce the friction and abrasiveproperties of the outer jacket (hydrophilic or hydrogel coatings must bewetted to reduce the friction and abrasive properties). Preferredpractical outer jacket materials are most often soft/elastomeric/lowmodulus in nature and have rather high coefficients of friction, whichmay make them difficult to insert into the vasculature and more abrasiveto the vasculature than desired, thus, requiring such coatings.Additionally, an irregular/bumpy/dimpled outer jacket OD and/or IDsurface is preferred to provide a more scattered echo reflection andthus facilitate imaging of the cylindrical shaft at angles that wouldnot produce a direct echo if the shaft were smooth. As a result of theouter jacket material choice, the reflection of sonic energy off theouter surface of the catheter shaft is reduced from that which otherwiseresults from a larger acoustic impedance mismatch between blood and thecatheter shaft outer jacket. Thus, the outer jacket layer couples moreof the ultrasonic energy into the catheter, so that a larger portion ofthe sonic energy penetrates the outer jacket layer and is transmittedthrough the catheter or into the shaft of the catheter and less sonicenergy is reflected from the surface of the outer jacket. In anotherembodiment, the outer jacket includes a material/filler (i.e. tungstenfillings) that improves the sonic energy dissipation properties of theouter jacket material to reduce the amplitudes of echoes reflected bythe internal portions of the catheter shaft. Sonic energy will passthrough the outer jacket to be reflected by the internal portions of thecatheter shaft and then back through the outer jacket again to bereceived by the imaging device and thus imaged. The more dissipative theouter jacket, the less of this sonic energy will be returned to theimaging device. In many embodiments, the material or filler included inthe outer jacket also causes the catheter shaft to more diffuselyreflect a portion of the sonic energy that penetrates the jacket back tothe imaging device, such that portions of the cylindrical catheter shaftthat do not produce a direct echo may be more easily imaged. Suchmaterials/fillers may also improve the imaging of the shaft by otherimaging modalities, such as fluoroscopy.

In outer jackets with irregular/bumpy/dimpled surfaces, it is preferredthat the thickness of the flatter surfaces of the jacket be kept nearthe ¼ wavelength thickness to reduce the amplitude of the directreflection. It should be noted that current ultrasonic imagingsystems/devices may filter out the lower frequencies to improve theresolution of the displayed image, called harmonic imaging, and whichtherefore affects the thickness of the quarter or three quarterwavelength outer jacket (a quarter or three quarter wavelength outerjacket thickness is twice as thick at 3 MHz than it is at 6 MHz). Ingeneral, an outer jacket thickness in the 0.001″ to 0.008″ range ispreferred. Below/near 0.001″ and coverage of metallic braids or otherinternal shaft components is uncertain and processing of the jackettubing becomes a challenge. Above/near 0.008″ and the jacket tends todisadvantageously increase the overall profile of the catheter. Anelastomeric jacket used to form the outer jacket layer has the propertyof being expandable (i.e. by air pressure), such that it may be easilyextruded as a tube with a wall thickness that is too thick, but thenexpanded and installed on a shaft in the expanded condition, whichreduces the wall thickness to a desired thickness.

By producing destructive interference between the reflected waves fromthe OD and ID surfaces of the outer jacket, the quarter or three quarterwavelength layer reduces the amount of directly reflected sonic energyfrom the catheter shaft surface that may be received by the ultrasonicimaging device. Thus, the quarter or three quarter wavelength matchinglayer reduces the displayed brightness of the catheter body image, tothereby avoid obscuring the image of the adjacent anatomy (e.g., cardiactissue) and avoid producing a pronounced curved body artifact asdiscussed in more detail below.

Unlike prior quarter wavelength matching layers provided on transducersto improve the transmission of sonic energy from the transducer into theblood and tissue of the patient's body (and also in the oppositedirection), a catheter embodying features of the invention has a quarteror three quarter wavelength matching layer extending along a section ofthe catheter shaft which is not an electrical to sonic energy and/or asonic to electrical energy transducer. Thus, catheter has a quarter orthree quarter wavelength matching layer which is specifically configuredto reduce the direct sonic reflections from a catheter shaft (and whichis not configured to more efficiently couple sonic energy into and outof a transducer).

In a presently preferred embodiment, the outer jacket is formed of amixture of two elastomeric compounds, styrene butadiene styrene andpolyurethane, which is extruded into a tube under conditions thatproduce an irregular and bumpy OD and a smooth ID. The jacket, wheninstalled on a catheter shaft, diffusely reflects sonic energy (lowamplitude), allowing the entire shaft covered by the jacket to be imagedand not just the shaft portions that produce a direct echo.Additionally, the direct echo portions of the shaft produce a muchreduced image brightness compared to conventional catheter shafts. Also,the jacket eliminates the ringing artifact from a metallic (e.g., NiTi)cage portion of the shaft located at the distal end of the shaft.

By reducing the amplitude of the direct echoes reflected by the cathetershaft and received by the imaging device, the curved body artifact ofthe catheter shaft is also reduced. Most ultrasonic imaging devicescontain an array of small ultrasonic transducers to send and receiveultrasonic energy to form images. These small ultrasonic transducerssend most of their sonic energy out in a direction that is generallyperpendicular to the surface of the transducer, but, especially in smalltransducers, a considerable amount of sonic energy also goes out inother directions in a manner commonly referred to as “side lobes”. Witha conventional highly reflective (high amplitude echo producing)cylindrical catheter shaft, the reflections of these side lobes thatreturn to the imaging device of a 3D echo system from the directreflecting surface portion of the catheter shaft produces a brightcurved image that may be mistaken for an image of the catheter shaft.Additionally, the bright curved image may obscure the images produced bythe relatively low amplitude diffuse echoes that may be received by theimaging device from other portions of the catheter shaft, and may alsoobscure the images of adjacent tissues. By reducing the amplitude of theechoes directly reflected by the catheter shaft, this bright curvedimage artifact is reduced in size and brightness, while the imagebrightness of the diffuse echoes from other portions of the shaft andfrom the tissues are less impacted (ultrasonic imaging systems aredesigned to amplify low amplitude echo signals more than higheramplitude echo signals).

One aspect of the invention is directed to a method of performing amedical procedure using a spherical distal tipped echogenic needlecatheter of the invention. The method generally comprises advancingwithin a patient's anatomy an echogenic needle catheter comprising anelongated shaft, a spherical distal tip which is preferably formed atleast in part of a conductive or metallic material and which has a portat a distal end of the spherical distal tip, and a needle which extendsdistally from the spherical distal tip port in an extendedconfiguration. The method includes directing sonic energy at thespherical distal tip from an ultrasonic imaging device, such that thespherical distal tip more diffusely reflects the sonic energy than atleast a portion of a non-spherical distal tip, to produce an ultrasonicimage of the distal tip within the patient.

It is preferred that the catheter be constructed in a manner that allowsthe catheter lumens to be flushed with water based solutions and avoidsair filled voids in the catheter shaft. In one embodiment, the methodincludes filling the catheter lumens with an aqueous fluid, so that thecatheter has a plastic-aqueous fluid interface which reflects less ofthe sonic energy than the plastic-air interface present in the absenceof the aqueous fluid. The plastic-air interface is a stronger reflectorof sonic energy than the plastic-blood or plastic-water interface. As aresult, the fluid-filled catheter of the invention reduces the amount ofsonic energy which is reflected back in the direction of the ultrasonicimaging device probe by enhancing the amount of sonic energy whichinstead penetrates the catheter and travels through the catheter to exitthe catheter on the other side of the catheter directed away from theultrasonic imaging device probe, and/or by enhancing the amount which isabsorbed by the catheter material and diffusely reemitted or dissipated.As a result, the catheter curved body artifact, which can be mistakenlyinterpreted as illustrating an arching or bending length of the catheterbody, is reduced. Thus, the standard Cath Lab practice of filling thecatheter lumen(s) with water-based solutions (usually heparinized salineor fluoroscopic contrast) prior to insertion into the body, althoughusually not sufficient to make a catheter's shaft reflect a sufficientlylow amplitude echo to eliminate or adequately reduce the curved bodyartifact, is nonetheless desirable for ultrasonic imaging.

An alternative embodiment is directed to an echogenic catheter, such asa needle catheter, with echogenic portions arranged in an array tofacilitate determination by ultrasonic imaging of the rotationalorientation of the catheter relative to a desired location within thepatient. In one preferred embodiment, the rotational orientationechogenic portions are on a transvascular needle catheter generallycomprising an elongated shaft having a needle lumen in communicationwith a needle distal port located proximal to the catheter shaft distalend, and a needle in the needle lumen configured for slidably extendingthrough the needle distal port in the catheter shaft. The rotationalorientation echogenic portions are more highly reflective than the shaftmaterial adjacent to the portions, and are arranged in an array in whicheach adjacent pair of portions are circumferentially and longitudinallyspaced apart from one another. The rotational orientation echogenicportion(s) oriented toward the ultrasonic imaging device probe willproduce the brightest image. The position of the ultrasonic imagingdevice probe relative to the ultrasonic image of the catheter is shownon the display along with the anatomy. As a result, the rotationalorientation of the catheter relative to the anatomy can be determined bythe ultrasonic image.

One aspect of the invention is directed to a method of performing amedical procedure generally comprising advancing within a patient's bodylumen an echogenic needle catheter having rotational orientationechogenic portions on an outer surface of a section of the cathetershaft, and determining the rotational orientation of the catheterrelative to a desired location in the body lumen by directing ultrasonicenergy at the shaft section from an ultrasonic imaging device. The sonicenergy produces an ultrasonic image of the shaft section in which therotational orientation echogenic portions do not all appear with anequal brightness for a given orientation. In a presently preferredembodiment, this is used to adjust the rotational orientation of atransvascular catheter's needle distal port within a patient's coronaryblood vessel, such as a coronary sinus, vein or artery, to direct theneedle into the desired heart tissue and avoid puncturing the free wallof the vessel or puncturing adjacent vessels. The array of rotationalorientation echogenic portions typically is formed by two or more, andmore preferably three or more echogenic portions. As a result, dependingon the circumferential spacing of the rotational orientation echogenicportions, multiple rotational orientation echogenic portions aretypically visible in any given ultrasonic image of the catheter but witha different brightness depending on the rotational orientation of theportions relative to the viewing direction of the ultrasonic imagingdevice. Thus, detailed rotational orientation information is obtainedfrom the ultrasonic image by comparing it to the known layout of thearray of rotational orientation echogenic portions. The catheter thusfacilitates adjusting the rotational orientation of the catheter withinthe patient, to accurately position the needle at the desired hearttissue, and avoid adjacent vessels or puncturing the free wall of thevessel.

Thus, one embodiment of the invention is directed to an echogeniccatheter configured to reduce or even out artifacts in the ultrasonicimage of the catheter (e.g., by correcting inaccuracies in the imageshape and/or location of the catheter or components of the catheter, inaddition to making the images less bright). In one embodiment, acatheter of the invention has a spherical distal tip which is directlyimaged over a range of angles (relative to the catheter) substantiallygreater than 180°. In another embodiment, an echogenic catheter of theinvention allows for the determination by ultrasonic imaging of therotational orientation of the catheter relative to the patient's anatomyby providing an array of portions of the catheter that have differentechogenic properties/image viewing properties. These and otheradvantages of the invention will become more apparent from the followingdetailed description and exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partially in section, of an echogenicneedle catheter embodying features of the invention, having a sphericaldistal tip.

FIGS. 2-4 are transverse cross sectional views of the catheter of FIG.1, taken along lines 2-2, 3-3, and 4-4, respectively.

FIG. 5 is a longitudinal cross sectional view of an alternativeembodiment of the spherical distal tip having a hypotube connectingmember.

FIG. 6 is a transverse cross sectional view of the catheter of FIG. 5,taken along line 6-6.

FIG. 7 is an elevational view, partially in section, of a distal endsection of an alternative spherical distal tip configuration.

FIG. 8 illustrates the catheter of FIG. 1 within a left ventricle of apatient's heart.

FIG. 9 is an elevational view of an alternative echogenic needlecatheter embodying features of the invention, having rotationalorientation echogenic portions on an outer surface of the cathetershaft.

FIG. 10 illustrates an enlarged, longitudinal cross sectional view ofthe catheter of FIG. 9, taken within circle-10.

FIG. 11 is a transverse cross sectional view of the catheter of FIG. 9,taken along line 11-11.

FIG. 12 illustrates the direct reflection of sound waves from anultrasonic imaging probe relative to a transverse sectional perspectiveview of the catheter of FIG. 9 taken through portion 72 a and lookingproximally so that the proximally spaced portions 72 b-d are alsovisible.

FIG. 13 is a representation of the displayed 3D ultrasonic image of asection of the catheter of FIG. 9 by an ultrasonic imaging device probeoriented relative to the catheter as shown in FIG. 12.

FIG. 14 is a representation of the displayed 3D ultrasonic image afterrotation the catheter 45° in the direction of the arrow shown in FIGS.12 and 13.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a needle catheter which embodies features of theinvention. In the embodiment illustrated in FIG. 1, the needle catheter10 comprises an elongated shaft 11 having a proximal shaft section and adistal shaft section and a needle lumen 15, and a spherical distal tip14 at the distal end of the shaft 11. A needle 16 is slidably disposedwithin the needle lumen 15 of the shaft, with an extended configurationin which the needle distal end extends distally from the distal end ofthe shaft (see FIG. 1), and with a retracted configuration (not shown)in which the needle distal end is proximally retracted into the catheterlumen. In the illustrated embodiment, the catheter 10 has a deflectionmember 17 (e.g., a tendon wire) connected to a deflection controlmechanism 18 at a proximal adapter 19, for deflecting the distal end ofthe catheter 10. To effectively deflect the distal end of the catheterthe deflection member 17 is preferably near the surface of the shaft inthe deflecting (curving) portion. However, a catheter having a sphericaldistal tip in accordance with the invention can have a variety ofsuitable catheter configurations including a non-deflectingconfiguration. The proximal adapter 19 on the proximal end of the shafthas a port 20 configured for providing access to the needle 16 fordelivery of an agent, or for aspiration, through the lumen of the needle16. A variety of operative connectors may be provided at the proximaladapter depending on the desired use of the catheter 10. FIGS. 2-4illustrate transverse cross sectional views of the catheter 10 of FIG.1, taken along lines 2-2, 3-3, and 4-4, respectively.

In the embodiment of FIG. 1, the shaft comprises a tubular body member21, which in one embodiment has a relatively flexible distal portion 52and a relatively less flexible proximal portion 51. A variety ofsuitable catheter shaft designs can be used with the spherical distaltip of the invention, including deflectable needle catheter shaftsdescribed in U.S. Ser. No. 10/676,616, incorporated by reference hereinin its entirety. The proximal portion 51 is typically formed at least inpart of metal, such as a polymer reinforced with a braided or coiledmetallic filaments or a hypotube or slotted metallic tube, although itmay alternatively or in addition consist of a high modulus polymer. Inthe illustrated embodiment, the shaft 11 has a braided body layer 23extending distally from a proximal end section of the catheter, andcomprising a polymeric material encapsulating a wound tubular supportlayer typically formed of braided filaments of a metal such as stainlesssteel. The braid is encapsulated by an outer layer which is typicallyformed of multiple sections of differing durometers/polymers joined endto end to provide a stiffness transitions along the length of thecatheter. The braid is formed over a polymeric core layer 24.

In the illustrated embodiment, the distal portion 52 of the tubular bodymember 21 of the shaft 11 comprises a cage typically formed of a slottedmetallic tube. The compression cage 22 is configured to deflectlaterally as discussed in the '616 application, incorporated byreference above. The cage 22 is typically covered with an outer jacketlayer 50, which in one embodiment is an impedance matching quarterwavelength layer as discussed in more detail below. In otherembodiments, the cage 22 may be a wire, wires, a construction of wires,a thin metallic strip(s) or a combined construction that provides arestoring force to the deflection distal section of the shaft 11.

An inner tubular member 26 extending within the tubular body member 21defines the needle lumen 15 of the shaft. The inner tubular member 26 isformed of a single layered, integral one-piece tube extending from theproximal to the distal end of the catheter, or alternatively of multiplesections of tubing with communicating lumens, and/or a multilayeredtube(s). The deflection member 17 extends within a lumen of a secondinner tubular member 25, and is secured to the shaft adjacent to thedistal end of the distal portion 52 of tubular body member 21. In theillustrated embodiment, a stabilizing tubular member 27, typicallycomprising a dual lumen extrusion, is positioned within at least asection of the cage 22 to stabilize the position of the inner tubularmembers 25, 26 therein. The stabilizing member 27 is formed of a singlesection or multiple longitudinally adjacent sections of the tubing, andhas a proximal end typically located within the cage 22 or a shortdistance proximal thereto. In one embodiment, the acoustic impedance ofboth the outer jacket and distal catheter shaft polymers (polymermixtures) is adjusted using tungsten filings to attain both a low directresultant reflected echo amplitude, but also the desired visibilityunder fluoroscopy. The stabilizing tubular member 27 may be processed inconjunction with the cage 22 such that the cage 22 is coated or coveredby the material of the stabilizing tubular member 27. This coating orcovering of the metallic cage 22 (or wire(s) or strip(s)) provides amore even acoustic impedance (places where metal is versus places wheremetal isn't) to the inside of the shaft for the outer jacket 50 to bematched to, as will be discussed in more detail below. In alternativeembodiments, the stabilizing tubular member 27 is omitted.

The catheter spherical distal tip 14 extends distally of the distalouter surface of the shaft, and has a spherical portion 30 and aproximal support portion 31 which has a proximal end connected to thedistal end of the distal portion 52 of tubular body member 21. In apresently preferred embodiment, a proximal end section of the distal tip14 is bonded, for example using an adhesive, to the inner surface of thecage 22, although a variety of suitable configurations can be used toattach the spherical distal tip including a spherical distal tip formedintegrally with the shaft 11.

The spherical portion 30 has a curving outer surface extending aroundthe circumference of the distal tip to an included angle substantiallygreater than 180°. The outer diameter of the spherical distal tip 14 isa rigid (i.e., non-collapsing/expanding) outer diameter, which istypically approximately equal to the outer diameter of the distalportion 52 of the tubular body member 21 to provide the greatest rangeof imaging angles. The spherical distal tip 14 has a lumen extendingthere through which forms a distal section of the needle lumen 15 andwhich is in communication with a port 28 at a distal end of thespherical distal tip 14. In the embodiment illustrated in FIG. 1, adistal section of the inner tubular member 26 defines the lumen withinthe spherical distal tip 14. However, a variety of suitableconfigurations may be used including an embodiment in which the distalend of the inner tubular member is proximal to the distal end of thecatheter.

In the illustrated embodiment, the proximal support portion 31 has aconically shaped section with an outer surface tapering distally to asmaller outer diameter. The support portion 31 is formed of asufficiently strong material(s) to securely connect and support thespherical distal tip 14 during use of the catheter 10. The length andtapering angle of support portion 31 is preferably chosen such that itwill not shield or block the spherical distal tip portion 30 from sonicenergy over the designed range of distal tip imaging angles.Additionally, the spherical distal tip portion 30 and support portion 31are configured to avoid catching on portions of the anatomy (i.e. valveto papillary muscle chordae) or on portions of the insertion devices(i.e. an introducer, a guide catheter) during positioning or withdrawal.Specifically, the tapers and curved surfaces of the spherical distal tipportion 30 and support portion 31 are designed limit the forces that maybe applied to the anatomy or other devices by the spherical distal tip14 before the catheter deflects enough to disengage from theobstruction.

In a presently preferred embodiment, the tip assembly is insert moldedof a polymer/plastic 33 around a high strength support member such as amachined hollow pin 34 (see e.g., FIG. 1), or short length of stainlesssteel hypotube 35 with a flared end at/near the center of the sphericaltip (see e.g., FIG. 5). The plastic material 33 is a damping material todissipate sonic energy at the tip 14. The conical portion 31 of the tipassembly is typically molded from the same material as the sphericalportion 30, and a portion of the pin 34 or hypotube 35 extendsproximally out of it.

Once mounted on the catheter, the proximal end of the pin 34 or hypotube35 resides inside the catheter shaft 21 and attaches the tip assembly tothe distal end of the catheter shaft. Thus, while the tip assembly has asubstantial metallic portion (i.e., the pin 34 or hypotube 35), it iscovered and in contact with a plastic that has damping qualities, and ithas at least a section not exposed directly to the sonic energy, tolimit its impact on the ultrasonic imaging of the tip. The catheter tip14 is configured for mechanically strong, secure attachment and support,while nonetheless minimizing the amount of metal at the catheter distalend in order to minimize the brightness and duration of the tip pyramidartifact in the ultrasonic image of the catheter distal end.

The spherical distal tip 14 preferably functions as an electrode, andthus has a conductor (e.g., a metal wire) electrically connectedthereto. In the embodiment illustrated in FIG. 1, the deflection member17 is electrically connected to the pin 34 so that the member 17 doublesas a deflection and a conduction wire. However, a variety of suitableconfigurations can be used including embodiments in which a separateconduction wire is provided which extends the entire length of thecatheter or which extends between the deflection member and thespherical distal tip. Therefore, it should be understood that inalternative embodiments, the shaft 11 may include a separate conductorlumen extending within the tubular body member 21. The conduction wireis soldered, welded, mechanically crimped or imbedded or otherwiseelectrically connected to the spherical distal tip 14.

Although not illustrated, at least a second electrode is typicallyprovided on the shaft 11, with a corresponding electrical conductor. Thesecond electrode, functions, for example, as a reference electrode forthe spherical distal tip electrode. The second electrode is preferablyprovided on the proximal portion 51 of the tubular body member 21 sothat it is located out of the heart chamber, preferably superior to theheart chamber, such as in the aortic arch or a vena cava, for tip tissuecontact/tissue ECG monitoring applications and/or about one centimeterbehind the tip for ECG anomaly detection applications. In applicationswhere pacing is anticipated to be required, many electrodes may bespaced along the distal portion of the catheter shaft, such that, atleast, one electrode (with a surface electrode) or electrode pair willpace successfully at the current catheter position. The conductorwire(s) electrically connect to an electrical connector 41 which isprovided at the proximal adapter 19 for connecting the catheter 10 todiagnostic or therapeutic equipment (not shown).

In the embodiment illustrated in FIG. 1, the metallic pin 34 has aproximal end 36 electrically connected to the deflection/conductormember 17 and has an exposed distal end at the distal end of thespherical distal tip 14 to form the distal tip electrode. The pin 34 hastwo grooves (illustrated with broken lines in FIG. 1) on opposite sidesof the proximal section of the pin 34, and the distal end of thedeflection/conductor member 17 is within one of the grooves.

FIG. 5 illustrates an alternative embodiment in which spherical distaltip 14 b has a hypotube 35 which does not have an exposed distalsurface. As a result, to function as an electrode, at least a portion ofthe outer surface of polymeric layer 33 of the tip 14 b is coated orotherwise provided with a conductor (metallic) outer layer(s) such as,for example, a gold outer layer and a copper inner layer. The conductor(metallic) coating is very thin, and is not illustrated in FIG. 5. Thethin metallic coating(s) on the tip has too little mass/size to storemuch sonic energy, and is also in contact with the damping plastic, andis so thin that a part of its reflective properties are determined bythe properties of the plastic behind it. The thin metallic coating(s)(not shown) form a wall preferably having a spherical outer surface, anda spherical inner surface defining a spherical interior chamber, withthe plastic 33 filling the spherical interior chamber around the needlelumen of the spherical distal tip. FIG. 6 illustrates a transverse crosssection of the tip 14 b of FIG. 5, taken along line 6-6.

In the embodiment illustrated in FIG. 5, a separate conduction wire 40is electrically connected to the hypotube to electrically connect to theouter conductor (metallic) coating. A band 41, typically formed ofmetal, connects the deflection member 17 between the hypotube 35 and thecage 22, in the illustrated embodiment. Although not illustrated in FIG.5, the shaft would typically include a needle 16 in inner tubular member26, and one or more additional inner tubular members, which are similarto inner tubular member 25 of FIG. 1, and which contain the deflectionmember 17 and/or conduction wire 40 in the embodiment of FIG. 5.

FIG. 7 illustrates a longitudinal cross sectional view of an alternativeembodiment of a spherical distal tip 14 c embodying features of theinvention, having a wall formed of a mixture of a polymeric material anda metallic material 42. The mixture is blended or otherwise combined andcomprises a sufficient amount of metallic material 33 so that thespherical distal tip 14 functions as an electrode when electricallyconnected to diagnostic or therapeutic equipment. In a presentlypreferred embodiment, the polymer/metallic material mixture has about80% to about 98% metallic materials 33 by weight. A variety of suitablematerials can be used including metallic materials 33 selected from thegroup consisting of tungsten, tungsten iridium, stainless steel, gold orplatinum and a variety polymeric materials are suitable including thoseselected from the group consisting of epoxies, silicones andthermoplastics.

In the embodiment of FIG. 7, the wall of the distal tip 14 c has aspherical outer surface and an inner surface defining a needle lumen 43within the spherical distal tip, so that the tip 14 c has a thickenedwall portion which fills the space between the needle lumen 43 thereinand the spherical outer surface of the distal tip 14 c. The lumen 43defined by the wall is configured for being in communication with aproximal section of the needle lumen 15 of the inner tubular member 26,or, alternatively, for receiving a tubular member such as a distalsection of the inner tubular member 26 or a separate tubular member.

Thus, in the embodiment illustrated in FIG. 7, the polymer/metallicmixture is molded or otherwise shaped to form the spherical distal tipwall extending from the outer to the inner surface of the tip 14.Alternatively, the metal/polymer mixture can be used to form an outerlayer on a spherical distal tip similar to the embodiment discussed inrelation to FIG. 5. Polymer/metal mixtures which contain a sufficientamount of polymer to facilitate working with the mixture typically donot contain a sufficient amount of metal to be conductive. Therefore, Ina presently preferred embodiment, such polymer/metallic materialmixtures are made conductive by first mixing the metallic material withthe polymer or the polymer parts while the polymer or the polymer partsare in a liquid state, and the non-conductive mixture is then applied tothe spherical tip, and the tip is subjected to heat and pressure in amold constructed to allow the polymer to flow out of the mold while mostof the metallic material is retained within the mold. In this way theconcentration of the metallic material is raised to the point that manyof the metallic material particles contact each other and thus, aconductive layer is former on the spherical tip (or also on otherportions of the tip). Several cycles of the addition of thenon-conductive mixture and the re-application of heat and pressure maybe required in some processes to create a conductive tip of the desiredshape and dimensions.

The spherical distal tip 14 has a uniformly curving outer surfaceextending around the circumference of the tip 14. The outer diameter ofthe spherical distal tip 14 is preferably equal to or less than theouter diameter of a portion of the shaft 11 which defines the distalouter surface of the shaft proximally adjacent to the spherical distaltip 14 (although the outer diameter of the spherical portion 30 of thedistal tip 14 is greater than a distal section of the conically shapedportion 31). Minimizing the outer diameter (OD) of the distal tip 14 sothat it is not greater than the OD of the catheter shaft is preferablein order to minimize the size of the introducer (OD/ID) required at thecatheter insertion site which has to accommodate the catheter therein. Alarger introducer OD causes a larger puncture wound, which studies haveshown have a greater incidence of complications such as pain, bleeding,infection and extended healing times. Typical catheters used to injectsubstances may range in size from about 4F (about 1.3 mm OD) for vesselneedle or other injections to about 9F (about 3 mm OD) for ventricularneedle or other injections. The spherical portion 30 of the distal tipmay have a smaller radius than catheter body radius to help minimize thebrightness and duration of the echo and tip pyramid artifact of theultrasonic image, however; all other things being equal, the smaller theradius of the spherical distal tip, the smaller the range of angles fromwhich that tip may be imaged.

Although generally not preferred due to concerns regarding effectivesterilization, an alternative spherical distal tip (not shown) can havea hollow structure with a spherical wall defining a hollow interiorchamber (i.e., not filled with plastic 33) and optionally formed ofmetal or a polymer-metal blend to function as a distal tip electrode.

FIG. 8 illustrates the needle catheter 10 with the distal end of thecatheter 10 within the left ventricle 45 of the patient's heart 46. Thecatheter 10 is typically advanced in a retrograde fashion within theaorta 47, via the lumen of an introducer sheath which is inserted intothe femoral artery. The catheter 10 illustrated in the embodiment ofFIG. 1 is not configured for advancement over a guidewire, although inalternative embodiments and delivery sites, such as into veins orarteries, a guidewire lumen is provided in the shaft 11 for slidablyreceiving a guidewire therein. Additionally, in such vesselapplications, the guidewire and catheter may be inserted into positionusing a guiding catheter that is first inserted into the introducer. Inthis intracardiac application, a deflecting mechanism is desired. Byactivating the deflection member 17 using the deflection controlmechanism 18 the distal end of the catheter is caused to deflect awayfrom the longitudinal axis of the shaft 11. With the distal end of thespherical distal tip 14 thus positioned in contact with a desired siteof the ventricle wall, electrical data can be collected from thespherical distal tip electrode 14. The electrical data (e.g., tissuecontact ECG) facilitates tissue diagnostics (in combination with echoimage ventricle wall motion measures) to determine if the site should betreated or not. The site can be treated by direct injection of atherapeutic agent, such as a biological or chemical agent, from theneedle 16. FIG. 8 illustrates the distal end of the spherical distal tip14 and the port 28 against the ventricle wall, with the needle 16 in theextended configuration advanced out the port 28 and into the cardiactissue 48 of the ventricle wall. Multiple sites within the leftventricle can be thus accessed and treated using the catheter of theinvention.

Although illustrated in the ventricle, a catheter of the invention canbe used to inject into the vessel wall or through the vessel into themyocardium or other adjacent tissues. Thus, although the distal needleport 28 is in the distal-most end of the spherical distal tip 14 coaxialwith the longitudinal axis of the catheter in the embodiment of FIG. 1(with the needle extending aligned with the longitudinal axis of thecatheter), in alternative embodiments (not shown; e.g., those forinjecting into or through a vessel) the catheter 10 has a needle portconfigured to direct the needle at an angle away from the longitudinalaxis of the catheter. For example, the port through which the needleextends can be located eccentric to the longitudinal axis of thecatheter or in a side wall of the catheter proximal to the distal end ofthe spherical distal tip.

Ultrasound can be used in conjunction with the catheter supplied ECG toprovide tissue diagnostics by visualization of the wall motion andthickness. Additionally, the catheter 10 facilitates using ultrasonicimaging for visualization and positioning of the catheter 10.Specifically, with the catheter 10 distal end in the left ventricle (orother desired location within the cardiac anatomy), sonic energy isdirected at the spherical distal tip 14 from an ultrasonic imagingdevice (not shown). The ultrasonic imaging device is typically anexternal device, a TTE probe (Transthoracic Echo, probe on the chest),although a TEE probe (Transesophageal Echo, probe in the throat), an ICEprobe (Intracardiac Echo, probe in a cardiac chamber) or an IVUS(Intravascular Ultrasound, probe in a vessel) can alternatively be used.

The spherical distal tip 14 reflects the sonic energy more diffuselythan a non-spherical tip, to provide an ultrasonic image of the distalend of the catheter from a wide range of angles relative to the viewingdirection of the ultrasonic imaging device. Additionally, the sphericaldistal tip 14 formed of a polymeric and metallic materials uses lessmetal in the distal tip than a solid metal distal tip or band electrode,and the metallic portions are in contact with the sonic energy dampingplastic material 33, so that the tip pyramid artifact has a desired lowlevel of brightness and shorter duration or is absent entirely from thedisplay.

In one embodiment, during ultrasonic imaging of the catheter 10, one ormore of the lumens of the catheter shaft are filled with an aqueousfluid so that a plastic-aqueous fluid interface is formed which reflectsless sonic energy than a plastic-air interface. Specifically, theultrasonic image is produced with the aqueous fluid within the needlelumen 15 of the shaft. In embodiments having one or more additionallumens, in addition to the needle lumen 15 of the shaft, the one or moreadditional lumens are preferably also filled with the aqueous fluidduring ultrasonic imaging. For example, the lumenal space, if any, ofthe tubular body member 21, between the inner surface of the tubularbody member 21 and the outer surface of the inner tubular members 25,26, is preferably filled with the aqueous fluid during ultrasonicimaging.

In a presently preferred embodiment, the catheter 10 has an impedancematching outer jacket layer 50 on an outer surface of at least a portionof the shaft 11, configured to decrease the reflected wave ultrasonicsignal of the catheter. The impedance matching outer jacket layer 50typically extends along at least a portion of the distal section of theshaft, and preferably is not provided on the proximal section 51. In theillustrated embodiment, the layer 50 has a distal end located proximalto the conical portion 31 and the spherical portion 30 of the sphericaldistal tip 14. The layer 50 is formed of a polymeric material, which inone embodiment is selected from the group consisting of a low densitypolyethylene (LDPE), EVA, or elastomers including neoprenes, silicones,SBS's (linear styrene-butadiene-styrene triblock copolymers, SB's(Radial styrene-butadiene block copolymers), SIS's (linearstyrene-isoprene-styrene triblock copolymers), butadienes andpolyurethanes. In an embodiment in which the layer 50 is formed of anelastomer such as polyurethane, a lubricious surface coating (not shown)is typically provided on an outer surface of layer 50 to decrease therelatively high friction of the elastomer. Although not illustrated, theouter jacket layer 50 preferably has an irregular wall thickness forminga rough outer surface.

In the embodiment illustrated in FIGS. 1 and 5, the outer jacket layer50 is on an outer surface of the compression cage 22, with a proximalend bonded to a distal end of the multilayered braid reinforced body ofthe proximal shaft section. In one embodiment, the layer 50 is fusionbonded to an underlying polymeric layer (not shown) formed of acompatible polymer. For example, in one embodiment, the layer 50 isformed of LDPE, and an underlying polymer layer forming part of thedistal section 52 of the tubular member 21 is formed of a high or mediumdensity polyethylene (HDPE, MDPE). However, the layer 50 canalternatively be friction fit onto the shaft, as for example in theembodiment in which the layer 50 is formed of an elastomeric materialsuch as polyurethane, and the elastomeric layer 50 is applied byallowing a temporarily expanded the layer 50 to retract down onto theshaft 11.

The impedance matching outer jacket layer 50 has an acoustic impedancewhich is between an acoustic impedance of blood and an acousticimpedance of the adjacent layer of the section of the shaft underlyingthe outer jacket layer, such that it more closely matches the acousticimpedance of the blood than does the polymeric material forming theouter layer along the distal section 52 directly underneath the outerjacket layer 50. For instance, the acoustic impedance of blood is about1.4×10⁵ gram/(cm²sec), silicone is about 1.6×10⁵ gram/(cm²sec), softpolyurethane is about 1.8×10⁵ gram/(cm²sec), HDPE is about 2.2×10⁵gram/(cm²sec) and stainless steel is about 46×10⁵ gram/(cm²sec). Thelarge mismatch between the acoustic impedance of the material(s) formingthe distal section 52 (i.e., in the absence of the layer 50), wouldcause a large proportion of the ultrasound wave to be reflected off theblood/catheter interface. The impedance matching outer jacket layer 50is formed of a material which provides an intermediate impedance betweenblood and the material forming the distal section 52, so that at eachmaterial interface there is less mismatch, and more of the ultrasoundwave propagates forward, rather than reflecting backward.

The impedance matching outer jacket layer 50 preferably has a thicknessof a quarter or three quarter wavelength of the center frequency of theultrasound waves emitted by the ultrasound imaging device or displayedby the ultrasonic imaging system, so that destructive interferenceoccurs between the reflected waves from the outer and inner surfaces ofthe jacket layer 50. The acoustic properties (e.g. acoustic impedance)of the outer jacket layer 50 (and/or the inner portions of the distalcatheter shaft 11) may be chosen or adjusted such that the amplitudes ofthe reflected waves from the outer and inner surfaces of the jacketlayer 50 are more equal and thus destructively interfere to produce alower amplitude resulting reflected echo. Such adjustments may be madeaccording formulas relating acoustic impedance to acoustic reflectionand relating the physical properties of materials and mixtures to theiracoustic impedance, as are well known in the art. The quarter or threequarter wavelength, impedance matching outer jacket layer 50 facilitatesproducing an ultrasonic image of the catheter shaft 11 at theperpendicular (direct echo) viewing direction which is notdisadvantageously bright, to minimize the catheter curved body artifactin 3D echo systems.

The thickness of the quarter or three quarter wavelength layer isdetermined based on the speed of sound in the polymeric material of thelayer and the desired frequency setting of the ultrasonic imagingdevice. For example, in one embodiment, the quarter wavelength impedancematching layer 50 is selected from the group consisting of apolyethylene layer having a thickness of about 0.0049 inches, and apolyurethane layer having a thickness of about 0.0044 inches, for usewith ultrasonic imaging at a center frequency of 4 MHz. It should benoted that the values given above are typical of LDPE and softpolyurethanes, however, there are many polyurethane and polyethyleneformulations that have a different sound velocity properties.

FIG. 9 illustrates an elevational view of an alternative needle catheter60 embodying features of the invention, having rotational orientationmarkers. In the embodiment of FIG. 9, the transvascular needle catheter60 generally comprises an elongated shaft 61 having a proximal section,a distal section, and a needle lumen 65 (see FIG. 11) in communicationwith a distal port 67 which is in a side wall of the distal shaftsection and which is spaced proximally from the distal end of thecatheter, and a needle 66 slidably disposed in the needle lumen.Although not illustrated, the shaft 61 typically has reinforcements,such as metallic braided reinforcing filaments embedded in the polymericmaterial of the wall of the shaft 61. FIG. 9 illustrates the needle inan extended configuration, extending out the port 67 away from thelongitudinal axis of the catheter 60. A proximal adapter 69 on theproximal end of the shaft has a port 70 configured for providing accessto the needle 66 for delivery of an agent, or for aspiration, throughthe lumen of the needle 66. A variety of operative connectors may beprovided at the proximal adapter depending on the desired use of thecatheter 60. The catheter 60 can have a variety of suitable shaftconfigurations and/or operative distal ends, as are conventionallyknown. For example, for details regarding suitable transvascular needlecatheter designs suitable for use with embodiments of the invention, seeU.S. Pat. Nos. 6,283,947; 6,692,466; 6,554,801; and 6,855,124,incorporated by reference herein in their entireties. For example, inone embodiment (not shown), a distal end portion of the needle lumenextends along a proximal tapered section of the inflated balloon suchthat the extended needle is directed away from the longitudinal axis ofcatheter shaft.

The catheter shaft 61 has marker bands 71 on at least the distal section62, which in a presently preferred embodiment are formed of a materialhaving echo reflective properties which are different (preferably morehighly reflective) than the adjacent portions of the catheter shaft. Forexample, in one embodiment the marker bands 71 are formed of a metal ora polymer/metallic material mixture. The marker bands 71 may or may alsonot be visible under fluoroscopy.

A plurality of rotational orientation portions 72 a-72 d are on an outersurface of the catheter shaft 61, and are formed of a material havingecho reflective properties which are different (preferably more highlyreflective) than the adjacent portions of the catheter shaft. In apresently preferred embodiment, the rotational orientation echogenicportions 72 are formed of the same material as the marker bands 71, suchas a metal (i.e. gold, tungsten, tungsten-iridium), a higher acousticimpedance polymer, or a metal filled polymer. Thus, portions 72 may, oralternatively may not, additionally be visible under fluoroscopy. In theembodiment shown in FIG. 10, illustrating an enlarged partiallongitudinal cross section of the catheter of FIG. 9, taken withincircle-10, the rotational orientation echogenic portions 72 are formedof a mixture of a polymeric material and a metallic material 74. Thepolymeric/metallic material mixture facilitates bonding the portions 72to the outer surface of the polymeric shaft 61, as for example byadhesive or preferably by fusion bonding. Alternatively, portions 72 mayconsist of metal, and in one embodiment (not shown), portions 72 formedof metal are soldered or otherwise connected to a metallic braidedreinforcement within the polymeric wall of the shaft 61 for secureattachment.

In a presently preferred embodiment, the portions 72 a-d all have thesame size, shape, and material composition configured to produce an echo(image) on the ultrasonic image of the catheter which is not overlybright. The relative thickness of the rotational orientation echogenicportions 72 may be somewhat exaggerated in the figures for ease ofillustration, and is preferably selected to avoid disadvantageouslyincreasing the profile of the catheter. The rotational orientationechogenic portions 72 typically have a thickness of about 0.001″ toabout 0.008″ and a length/width of about 0.010″ to about 0.040″, and mayproject slightly above the outer surface of the shaft 61 or be wholly orpartially recessed within the outer surface (e.g., jacket layer) of theshaft 61, and are preferably slightly recessed below the outer surfaceof the shaft.

In a presently preferred embodiment, the shaft has an outer polymericjacket layer with holes in it in which the rotational orientationechogenic portions 72 are placed and bonded to the shaft, and theportions 72 are formed of a metal, a metal filled polymer, or a highacoustic impedance plastic, with a curved outer surface to provide adirect image at the desired range of probe angles relative to thecatheter shaft. Such a configuration facilitates ultrasonic imaging ofthe shaft (due to the jacket), and determining proximal and distallocations from markers 71, and determining rotational orientation frommarkers 72 which are easily imaged when on the side of the catheterfacing the imaging probe.

FIG. 11 illustrates a transverse cross sectional view of the catheter ofFIG. 9, taken along line 11-11. In the illustrated embodiment, the shaft61 has an inflation lumen 62 and a guidewire lumen 63 in addition to theneedle lumen 65 of the shaft 61. In the illustrated embodiment, thecatheter 60 is configured for rapid exchange, with a guidewire 68slidably disposed in guidewire lumen 63 and through a guidewire proximalport spaced distally from the proximal end of the shaft. However, avariety of suitable catheter shaft designs can be used as areconventionally known. A balloon 64 on the catheter distal section has aninterior in fluid communication with the inflation lumen 62 forinflating the balloon. The inflated balloon 64 can be configured for avariety of suitable functions including to facilitate positioning theneedle distal port 67 of the shaft against the vessel wall, or to anchorthe catheter within the vessel lumen, or to occlude the vessel lumen.However, a variety of suitable shaft configurations can be usedincluding shafts which do not have balloon 64, inflation lumen 62,and/or guidewire lumen 63, or which have one or more addition lumenssuch as a fluid delivery lumen configured for delivery of fluid such asmedication or contrast agent to the patient from a port in the shaftdistal section. Similarly, in alternative embodiments, the shaft 61includes one or more additional needle lumens with additional needlesslidably disposed therein (not shown).

Under ultrasonic imaging, the distal most marker band 71 in theembodiment of FIG. 9 illustrates the longitudinal location of the needleport 67 of the shaft 61. However, because the marker bands 71 areuniform around the entire circumference of the catheter shaft 61, theultrasonic image of the marker bands 71 will appear irrespective of therotational orientation of the catheter. Practical injection needles 66are generally too small to reflect sound waves well enough to be imagedby echo systems. Also, the needle 66 is often shielded from the soundwaves by the catheter shaft 61. Thus, the needle 66 will not be seen/bedistinguishable in the ultrasonic image.

The rotational orientation echogenic portions 72 are arranged in anarray in which each adjacent pair of portions 72 are circumferentiallyand longitudinally spaced apart from one another. In the embodiment ofFIG. 9, four portions 72 a-d are proximally adjacent to the needle port67, and are circumferentially spaced apart in 90° intervals around thecircumference of the shaft. However, alternative numbers and spacingscan be used depending on factors such as the desired orientationdetermination performance characteristics of the catheter, theechogenicity and orientation of the portions 72, and the catheter shaftdesign. In a presently preferred embodiment, at least 4 portions 72 areprovided.

FIG. 12 shows a perspective transverse view of the catheter of FIG. 9,through portion 72 a, and looking proximally so that the proximallyspaced portions 72 b-d are also visible, to illustrate the directreflection of sound waves from an ultrasonic imaging probe 80. Theportion 72 a that is directly in the path of the sound wave and presentsa face surface that can directly reflect an echo back to the probe 80,will be imaged the brightest. The portion 72 c on the side of thecatheter opposite to the ultrasonic imaging probe 80 will produce adirect reflection, but because the sound waves that hit it and itsreflected echo must pass thru the catheter body, its echo will have asmall amplitude and be displayed much less bright (or not at all) thanthe portion 72 a (some of the sonic energy is reflected off the catheterbody/blood interface and some of the sonic energy is dissipated as heatin the plastic catheter body). The two portions, 72 b and 72 d, whichare 90 degrees from the portion 72 a (i.e., the face surface of eachportion 72 b and 72 d is oriented at 90 degrees from the path of thesound wave) will produce an echo directed away from the ultrasonicimaging device probe and will therefore not be imaged.

FIG. 13 is a representation of the displayed 3D ultrasonic image of asection of the catheter of FIG. 9 by the probe oriented as shown in FIG.12. Only portion 72 a with its most direct reflected echo shows up in adistinguishable manner in this representation. In alternativeembodiments, the other portions 72 b-d could be made distinguishable inthe view of FIG. 13, but will be much less bright than portion 72 a(e.g., using portions 72 formed of more highly echogenicmaterials/structural shapes, or different echo system display settings).FIG. 14 is a representation of what the same image in FIG. 13 would looklike if the section of the catheter in FIG. 13 were rotated 45° in thedirection shown by the arrow in FIGS. 12 and 13. In this case, bothportions 72 a and 72 d are in the direct path of the probe's sound wavesand are only 45° from the most direct reflection path shown in FIG. 12.Thus, they are equally bright, and brighter than portions 72 b and 72 c,but dimmer than portion 72 a was in FIG. 13 (the brightness beingrepresented in the figures by the degree of shading). In otherembodiments, the outer surfaces of the portions 72 could be curved suchthat 72 a and 72 d were equally as bright as portion 72 a was in FIG.13.

At least at 45° intervals in the embodiment of FIG. 9, the rotationalorientation of the catheter 60 relative to the probe 80 may be easilydistinguished by distinctive echo images of this section of the catheter60. Thus, the rotational orientation of the needle 66 (or any otherfeature locked to the catheter body) can be determined from the 3D echoimage. Additionally, the distal end of this catheter section isdistinguishable from its proximal end by the marker bands 71. Becausethe needle 66 is near the distal marker band 71, the location of theneedle 66 in the ultrasonic image is known. It should also be evidentthat, when in the patient's body, a 3D image of the patient's bodytissues would be present and thus, the location and direction of theneedle travel would be known relative to the imaged anatomy. This istrue in any projection, if the position/direction of the probe 80 isknown or indicated on the image. Thus, the catheter 60 facilitatesdirecting the needle 66 into the desired anatomy in the desireddirection by observing a 3D image display, and manipulating the catheter(rotational and/or longitudinal manipulations) as needed. It should alsobe evident that many modifications can be made to distinguish otherrotational orientation intervals or other catheter features. The numberand location of the rotational orientation echogenic portions 72 and thenumber and positions of marker bands 71 are selected to preferablyprovide incremental information regarding the rotational orientation ofthe catheter and the proximal and distal ends of the orientationindicating section of the catheter shaft. Thus, a small amount ofrotation produces a distinguishable change in the ultrasonic image ofthe array of portions 72, providing highly detailed information aboutthe catheter rotation. For example, the array of portions 72 of theembodiment of FIG. 9 would produce a different image depending onwhether the catheter was rotated 45° clockwise or counterclockwise.Additionally, due to the number and spacing of the rotationalorientation echogenic portions 72 in the embodiment of FIG. 9, thecatheter 60 does not have to be rotated to determine the rotationalorientation of the catheter in the patient's body, because one or moreof the portions 72 will be visible in an ultrasonic image of thecatheter.

In one embodiment, a method of the invention includes overlaying oralternating a 3-D echo image of a needle catheter of the invention withan image (such as a 3-D echo, 3-D biplanar fluoro or CT image) of thepatient's blood vessels adjacent to the needle catheter. The bloodvessel image is typically obtained using contrast injections into thearteries and/or veins. By overlaying or alternating the images, themethod thus avoids injecting the needle into the adjacent blood vesselsduring a procedure using a transvascular or intraventricular needlecatheter of the invention.

While the present invention is described herein in terms of certainpreferred embodiments, those skilled in the art will recognize thatvarious modifications and improvements may be made to the inventionwithout departing from the scope thereof. For example, the dampingfeatures of the distal tip electrode may be used to reduce theultrasonic imaging artifacts of other elements such as other electrodesor markers on the catheter. Additionally, while discussed primarily interms of a needle catheter, it should be understood that a variety ofmedical devices can be used which embody features of the inventionincluding surgical and implantable devices, and other catheters such asballoon catheters, guiding catheters, ablation catheters, devicedelivery catheters and catheters that accommodate or incorporate sensors(i.e. temperature, chemical, oxygen, etc.). For example, the needle canbe eliminated and solution infused through the empty lumen of thecatheter (e.g., to inject directly into the bloodstream just proximal ofthe area to be treated). Additionally, in vessel injection systems, thespherical tip will likely not need to function as an electrode, so theconduction requirement may be omitted.

Thus, the echogenic catheter features being disclosed are applicable toall types of catheters/other devices that may be guided by ultrasoundand/or must be present in the anatomy during ultrasonic imaging.Additionally, although the catheter features are useful for use with 2Dor 3D ultrasonic imaging systems, it should be noted that for thepurpose of catheter guidance, a 3D echo system is preferred to the“slice” image provided by a 2D echo system. A 2D echo system producesimages that are like viewing a very thin planar slice thru the anatomyand the catheter, making it extremely difficult to distinguish/find acatheter, follow a catheter to its tip or other relevant portion anddetermine where in the anatomy the relevant portion of a catheter islocated/oriented or is located/oriented relative to a previouslocation/orientation. A 3D echo system produces images that can eitherbe a see-through representation of large 3D volume of the anatomy andcatheter or a 3D surface image of the same. In a 3D image, anatomicreference points abound in the image and, with a properly echogeniccatheter (as described in this application), all portions of thecatheter in the image volume may be seen, and the direction of thecatheter shaft relative to the anatomy is easily visualized as describedherein.

Moreover, although individual features of one embodiment of theinvention may be discussed herein or shown in the drawings of the oneembodiment and not in other embodiments, it should be apparent thatindividual features of one embodiment may be combined with one or morefeatures of another embodiment or features from a plurality ofembodiments.

1. A method of performing a medical procedure, comprising: a) advancingwithin a patient's anatomy an echogenic needle catheter, comprising i)an elongated shaft having a proximal end, a distal end, and a needlelumen; ii) a spherical distal tip at the distal end of the elongatedshaft, having a lumen in communication with a proximal section of theneedle lumen of the shaft and with a port at a distal end of thespherical distal tip, wherein the spherical distal tip is in continuouscontact with the lumen; and iii) a needle in the needle lumen, whichextends distally from the spherical distal tip port in an extendedconfiguration, and which has a lumen; and b) directing sonic energy atthe catheter from an ultrasonic imaging system, such that the sphericaldistal tip more diffusely reflects the sonic energy than a nonsphericaldistal tip, to produce an ultrasonic image of the spherical distal tipdue to the spherical tip having an outer surface with a circumferenceangle substantially greater than 180 degrees, having a rigid outerdiameter wall with a curved outer surface formed at least in part of arigid polymeric material, and having the spherical distal tip formed atleast in part of an electrically conductive material.
 2. The method ofclaim 1 wherein the spherical distal tip is formed at least in part of ametallic material and is electrically connected to a conductor so thatthe spherical distal tip is an electrode.
 3. The method of claim 2wherein the spherical distal tip is formed in part of a damping plasticmaterial, and including dissipating the sonic energy within the dampingplastic material of the spherical distal tip, so that the ultrasonicimage of the distal tip has a less bright and long pyramid artifact thana metallic tip formed without the damping plastic material.
 4. Themethod of claim 1 wherein the catheter shaft comprises a proximal shaftsection and a distal shaft section, and including an electrode on theproximal shaft section a sufficient distance from the distal tip that anultrasonic image of the electrode does not over lap with the ultrasonicimage of the distal tip.
 5. The method of claim 1 wherein the cathetershaft has at least a section with an outer jacket layer having athickness of a quarter or three quarter wavelength of the ultrasoundwaves emitted by the ultrasound imaging system, the outer jacketcomprising a polymeric material with an acoustic impedance which isbetween an acoustic impedance of blood and an acoustic impedance of theadjacent layer of the section of the shaft underlying the outer jacketlayer, such that it more closely matches the acoustic impedance of bloodthan does an adjacent layer of the section of the shaft underlying theouter jacket layer, so that directing sonic energy at the catheterproduces a reflected wave ultrasonic signal of the catheter which isless than the signal produced by the catheter without the outer jacketlayer.
 6. The method of claim 1 including filling the needle lumen ofthe shaft with an aqueous fluid, so that the catheter has aplastic-aqueous fluid interface which reflects less of the sonic energythan a plastic-air interface, and the ultrasonic image is produced withthe aqueous fluid within the needle lumen of the shaft.
 7. The method ofclaim 1 wherein the shaft has one or more lumens in addition to theneedle lumen of the shaft, and including filling the one or more lumenswith an aqueous fluid, so that the catheter has a plastic-aqueous fluidinterface which reflects less of the sonic energy than a plastic-airinterface, and the ultrasonic image is produced with the aqueous fluidwithin the additional one or more lumens.
 8. The method of claim 1further comprising determining a location of the catheter within thepatient.
 9. The method of claim 1, wherein the echogenic needle catheterfurther comprises: (iv) a conductor electrically connected to thespherical distal tip and extending through the shaft to the proximalend. so that the spherical distal tip is an electrode, the conductorincluding an elongated deflection member with a distal end secured tothe shaft, configured for deflecting a distal section of the cathetershaft.